1. Field of the Invention
The present invention relates to a matrix type color electroluminescence (EL) display panel for a color display.
2. Description of the Prior Art
Since the discovery of electroluminescence (EL), obtained by applying an electrical field to zinc sulfide (ZnS), luminescent host material, a luminescent center to be added thereto and the like have been researched. As a result, a thin film EL device has been developed which includes a ZnS thin film to which manganese (Mn) is added as a luminescent center, dielectric (insulating) layers being provided on the top and bottom sides thereof and electrodes being further provided on the top and bottom sides thereof where the electrodes on at least one side are transparent. Such thin film EL device is characterized by its high brightness and long life and has therefore been incorporated as a thin and light display element into a display of a portable computer, a measuring device or the like.
A conventional EL display panel has a lamination structure comprising a glass substrate, transparent electrodes and a first insulating layer thereon, a luminescence layer, a second insulating layer and back electrodes. In such a display panel, the transparent electrodes and the back electrodes are formed in a plurality of columns and rows, respectively, that is, arranged as an X-Y matrix. Accordingly, applying voltage to an arbitrary pair of X and Y electrodes causes a point of coordinates (X, Y) to emit light. In this case, a method disclosed in Japanese Patent Publication No. 21795/1983 is generally available for the connection between the electrodes and an external drive circuit; that is, the electrodes are extended alternately to opposite ends of the substrate to broaden the distance between adjacent end portions of the electrodes.
FIG. 5 is a top plan view showing a prior art color EL display panel in which a plurality of row electrodes Yj and a plurality of column electrodes Rxi, Bxi, Gxi orthogonal thereto are formed on a substrate S. Voltage is applied to the respective electrodes Yj and Rxi, Bxi, Gxi so that the coordinates of intersecting points between them are caused to emit light. Three of the electrodes Rxi, Gxi, Bxi, which correspond to the luminescence layers R, G, B for the primary three colors, red, green and blue, make up an electrode for one pixel.
Generally, the color signals for red, green and blue are controlled on the basis of one pixel with regard to luminescent color and brightness with respective luminous intensities, and therefore all of the signals are collectively processed as one unit of information. However, when the luminescence layers for the three primary colors are formed in parallel as shown in FIG. 5, Rxi and Gxi (which make up one pixel together) are extended separately to opposite ends of the substrate. This causes complicated signal processing because signals for the same pixel must be processed separately and transmitted to the alternately-arranged input terminals.